Leg prostheses come in three general varieties: hip disarticulation prostheses comprising a socket, hip joint, knee joint and foot; above-knee prostheses comprising a socket, knee joint and foot; and below-knee prostheses comprising just the socket and foot. In each case, a stump or support socket, or just socket, to receive the leg stump must be fabricated and correctly aligned with the other prosthetic components that extend downward there from.
The conventional process of fabricating and fitting the stump socket is typically as follows: A check or test socket mold or model is cast from a malleable material, typically plaster or plastic, directly from the amputees stump. The check or test socket is fitted on the remaining prosthetic components for fitting or “trial walking”. During trial walking, the check socket is aligned with the adjacent prosthetic component using a jig, and the alignment marked. Through a process similar to the casting of a sculpture, a positive impression or model is cast from the check socket, and then the positive model is used to cast the definitive, or permanent, support socket. After fabrication of the permanent support socket, it becomes necessary to restore the alignment of the permanent socket with the other prosthetic components.
The fabricating process is labor intensive, time consuming, specialized and expensive. Competent orthotic technicians are highly skilled craftsmen with extensive training and experience. The fabrication, assembly and alignment process often involves trial and error and much depends upon the judgment and skill of the artisan fabricator.
Fabrication and proper assembly of the support socket is the most delicate and time consuming aspect of the leg prosthesis fabrication process. Support sockets made for above-knee prosthetics are larger, more difficult to fabricate, and less forgiving than those for below-knee prosthetics. In each case, however, re-alignment of the permanent socket with the lower orthotic components is necessary. Support sockets that are not properly shaped, or inexactly aligned, are uncomfortable to use and can cause damage or injury to the patient's stump, requiring that the socket be re-aligned or re-fabricated.
A number of inventions have been described having as their object the improved fabrication of lower limb prostheses. Most teach the use of computers and computer imaging to shape and/or orient the support socket, to fabricate the permanent socket, or to map or locate bony protuberances in the stump. Other inventions describe apparatus that facilitate the casting of the temporary socket or fabrication of the permanent socket. All such inventions have as their goal making the fabrication process less labor intensive, less time consuming, less expensive or more exacting.
One of the more time consuming and difficult aspects of the process of fabricating lower limb orthotic devices is the need to precisely re-align the permanent support socket with the adjacent structural component after the definitive socket is cast. The initial alignment is marked during the trial walking phase, but this alignment is lost when the check socket is transformed into a positive model and then transformed, a further time, into the permanent socket.
Presently the process of restoring the alignment of the definitive socket with the other prosthetic components is accomplished by transferring lines and points from the check socket, to the positive model, and then again from the positive model to the permanent socket. Due to the thickness and three-dimensional shape of the support socket, the process of transferring the reference points is difficult, cumbersome and time consuming. Drilling and the use of alignment benches or stands having screw adjusters are used to facilitate the process. Even with these aids, however, points are not transferred accurately, causing the resulting alignment to be inexact and requiring that the process be repeated or begun again. None of the prior art publications or commercially available apparatuses fully addresses the difficulty in restoring the alignment of the definitive support socket in the leg prosthesis fabrication process.
It is a primary object of the present invention to provide a method and apparatus to facilitate the restoration of alignment of the permanent support socket with the adjacent prosthetic component during the fabrication process. It is a further objection of the present invention to provide a method and apparatus to restore the alignment of the support socket of a leg prosthesis during the fabrication process that improves the precision of alignment, and that increases the speed and accuracy with which leg prostheses are produced while reducing the cost of their production. It is also an object of the present invention to provide a method and apparatus for the fabrication and re-alignment of multiple support sockets concurrently, using the same apparatus.